Being glucose intolerant / prediabetic, I used to drink several diet Cokes per day for years. Finally, the acids took their toll on my GI system and I developed IBS.

There have been several scientific studies that prolonged ingestion of aspartame can affect the brain. It's hard to quit diet sodas because they usually contain caffeine which is very addictive. Diet Coke was my happy juice for many years and it was hard to stop drinking it. Finally, I switched to unsweetened ice tea and now drink only that. I no longer have a caffeine addiction and my GI system is better. Do I miss the caffeine? Heck yeah. But, I am better off without it and the other chemicals in diet sodas (all sodas for that matter) that are potentially harmful including artificial colors, acids and the like.